1. Field of the Invention
The present invention relates to a battery module, and in particular to a rechargeable battery for constituting the battery module in which the internal battery resistance can be made small and the battery output can be increased.
2. Description of Related Art
FIG. 10 shows a conventional battery module made by connecting a plurality of rechargeable batteries and coupling them together as one so as to obtain the necessary power. In this battery module, a plurality of cells 41 (41a to 41j) made of sealed alkaline rechargeable batteries as shown in FIG. 11 are arranged side by side, with the long lateral walls of the battery cases 42 adjacent each other. End plates 52 are arranged against the outside of the cells 41a and 41j at both ends, and the two end plates 52 and 52 are bound together with binding bands 53 so as to couple the cells together as one piece.
For the cells 41, an electrode plate group 47, comprising positive electrode plates and negative electrode plates layered with intervening separators, thus constituting elements for electromotive force, is accommodated in a battery case 42 together with a liquid electrolyte, and the open end of the battery case 42 is closed with a lid 46 provided with a safety vent 45. From the upper end at one side of the positive electrode plates forming the electrode plate group 47, leads 49 extend upward and are connected to a positive electrode terminal 43 above them, and similarly, from the upper end of the other side of the negative electrode plates, leads 49 extend upward and are connected to an negative electrode terminal 44 above them. The positive electrode terminal 43 and the negative electrode terminal 44 are attached to the lid 46.
The positive electrode terminals 43 and negative electrode terminals 44 of coupled neighboring cells 41 are connected by connection plates 51, thereby connecting all cells 41 in series. When the battery cases 42 are coupled, ribs 48, which protrude vertically from the long lateral walls of the battery cases 42, are abutted against each other, forming coolant passages running in the vertical direction along the long lateral walls of the battery cases 42 in the space between ribs 48. The cells 41a to 41j are cooled by flowing air through these coolant passages.
However, with the configuration for the cells 41 of this conventional battery module, leads 49 extend from a portion at the upper end on one side of the electrodes and are connected to the electrode terminals 43 and 44, and consequently, there were the problems that the internal resistance of the battery was large, because the average distance from the surface of the electrodes to the collector portions of the leads 49 was long, and that the power output was low, because the utilization rate of the electrode active material was low.
Moreover, because the terminals 43 and 44 protruding to the outside of the lid 46 are connected by connection plates 51, it is necessary to provide space for this connection at the upper end of the battery cases 42. Furthermore, since the connection portions are exposed, there is the problem that the space for installing this battery module cannot be made compact.
Moreover, in the portions where electrode pillars of the electrode terminals 43 and 44 extend through the lid 46, O-rings for providing a seal are usually placed only on the inner side of the lid 46, and there was the danger that electrolyte may leak during use of the battery.
In view of these problems of the prior art, it is an object of the present invention to provide a rechargeable battery, of which internal battery resistance is small and of which battery output can be improved. A further object of the present invention is to provide a battery module, of which installation space can be made, and in which there is no danger of electrolyte leakage.
To achieve the above object, the present invention provides a rechargeable battery, comprising:
a prismatic cell case having short lateral walls and long lateral walls; and
a group of electrodes accommodated inside the cell case, the group of electrodes including a plurality of positive and negative electrode plates arranged alternately and substantially in parallel to the long lateral walls of the cell case with an intervening separator therebetween;
wherein lateral edges of the positive electrode plates protrude beyond the negative electrode plates on one side, and lateral edges of the negative electrode plates protrude beyond the group of positive electrode plates on the opposite side, the protruding portions forming lead portions.
Since the lateral portions on one side of the electrode plates serve as lead portions, the average distance from the surfaces of the electrode plates to the collector portions can be made short, the internal battery resistance can be made small, and the utilization rate of the electrode active material becomes large, whereby the power output of the battery can be increased.
The lateral edge portions of the negative electrode plate and positive electrode plate lead portions of the group of electrodes are attached to respective collector plates, and the group of electrodes is thus held by the collector plates. Therefore, the group of electrodes can be held with a compact configuration, and the surface area of the regions for generating an electromotive force can be made large, whereby the battery capacity can be increased.
The collector plates are provided with curved portions at both ends thereof for clamping the group of electrodes. Thereby, the electrodes do not spread and extend toward the outside of the collector plates when the group of electrodes are attached to the collector plates, and the electrodes can be fixed reliably to the collector plates.
By setting D less than L xe2x89xa64D, where L is the length of a side of the lead portions of the electrodes and D is the length of a side in a direction perpendicular thereto, the average distance from the surfaces of the electrode plates to the collector portions can be made even shorter, and the above-noted effects can be enhanced. If Dxe2x89xa7L, the ratio of the space for connecting the cells, that is formed between the upper edge of the electrode plate group and the upper wall of the cell case, against the volume of the electrode plate groups becomes large. As the proportion of the dead space increases, the battery capacity is compromised accordingly, but this problem can be solved when L and D are set as noted above. On the other hand, if L greater than 4D, the aspect ratio (vertical/horizontal) becomes too large, which leads to problems with regard to other structural conditions, such as maintaining the strength of the collector plates or manufacturing of the cell cases. Moreover, if L greater than 4D, there is the problem that temperature variations are large between the two ends of the electrode plate groups in the flow direction of the coolant when the outer walls of the cell case are cooled by letting a coolant flow in the longitudinal direction along the lead portions of the electrode plate groups, but this problem does not occur when L and D are set as noted above.
In the cell case in which a group of electrodes is accommodated, which is made of electrode plates whose dimensions are set to D less than Lxe2x89xa64D as noted above, by setting d less than l less than 4d, where l is the length of the long lateral walls of the cell case in the direction parallel to the lead portions of the electrodes, and d is the width of the long lateral walls in the direction perpendicular thereto, the proportion of the dead space is optimized and the battery capacity is increased. Moreover, the temperature variations between the upper portion and the lower portion of the electrode plates can be reduced, when the cell case is cooled by letting the coolant flow in the vertical direction of the long lateral walls of the cell cases.
As mentioned above, the lateral edge portions of the group of positive electrode plates protrude beyond the group of negative electrode plates on one side, and the lateral edge portions of the group of negative electrode plates protrude beyond the group of positive electrode plates on the opposite side form the lead portions. Therefore, a single, belt-like separator can be arranged in a zigzag fashion between the positive electrode plates and the negative electrode plates. In this way, the separator can be arranged easier between the electrode plates than by covering the electrode plates with bag-shaped separators.
The rechargeable battery according to the present invention can be constructed such that:
a plurality of cell cases are coupled together as one piece with the short lateral walls of the cell cases being mutually integrated, thereby constituting an integral battery case;
upper open ends of the cell cases are closed by an integral lid member; and
the collector plates in adjacent cell cases are connected to each other via a connection fitting that extends through the short lateral walls between the adjacent cell cases.
Thereby, the neighboring cells can be connected to each other inside the integral battery case, and the space for setting up the rechargeable battery can be made compact.
Furthermore, through holes are formed in the short lateral walls between two adjacent cell cases at an edge portion; and the connection fitting comprises a pair of frame fittings, each frame fitting having a base end and a protruding portion that is inserted into the through holes, the distal ends of the protruding portions being welded together, and the collector plates being attached to the base ends of the frame fittings. Thereby, the collector plates can be connected easily by welding with a pair of frame fittings.
According to the present invention, a battery module can be constituted by coupling a plurality of rechargeable batteries together, each of the rechargeable batteries, accommodating therein a group of electrodes and a liquid electrolyte, wherein:
a plurality of prismatic cell cases having short lateral walls and long lateral walls are arranged side by side, with adjacent short lateral walls being integral with each other;
the group of electrodes inside a cell case including a positive electrode collector plate and a negative electrode collector plate arranged at lateral opposite ends of the cell case in the direction of the long lateral walls thereof;
through holes are formed in the short lateral walls of the cell cases at upper edge portions thereof;
a pair of frame fittings comprising base ends and protruding portions are provided for each of the cell cases for connecting two adjacent cell cases, the protruding portions of the pair of frame fittings being inserted into the through holes formed in the upper edge portions of the short lateral walls of the cell cases from both sides and welded together, and the positive and negative electrode collector plates in the cell cases being respectively attached to the base ends of the frame fittings;
end frame fittings having base ends and protruding portions are provided for cell cases located at both outer ends of the rechargeable battery for connecting the cell cases at both outer ends of the rechargeable battery to outside terminals; and
connection terminals having protruding portions are connected to the end frame fittings of the cell cases at both outer ends of the rechargeable battery.
Thereby, the connection between the cell cases and the outside of the cell cases can be carried out easily with a compact configuration.
Moreover, a sealing material is provided around the protruding portions of the frame fittings and the connection terminals, so as to provide a seal between the two adjacent cell cases, whereby both sides of the connection configuration can be sealed double, and leakage of liquid electrolyte during use of the battery can be prevented.
While novel features of the invention are set forth in the preceding, the invention, both as to organization and content, can be further understood and appreciated, along with other objects and features thereof, from the following detailed description and examples when taken in conjunction with the attached drawings.